Can you explain the options for: "Which users do you want to allow to register?"

Everyone - On the login page, users will see a Register tab, where they can enter their email address and receive anautomated registration email.

Admin Invite Only - The Register tab is not available on the login page. A user must be “invited” to participate by anAdministrator, either by using the Invite field to invite one user at a time or through the Bulk Registrationprocess.

Users can invite new users - Only available when the WebStorm is set to “Everyone” as allowed to register (Admin Invite Only is notset).

Enables an Invite a Friend widget, which allows users to enter the email address of an unregistered user.